Electrical power sources have been developed for powering movement of vehicles such as cars. Because these vehicles have large power requirements, these power sources typically include several large batteries. However, difficulties associated with managing the thermal characteristics of large batteries can make these batteries impractical for use in powering vehicles.
An alternative to the use of large batteries is a battery pack that includes a collection of smaller individual batteries. One version of prior power packs connects several battery trains in series where each battery train includes a plurality of batteries in series. Because the batteries in a series discharge differently, it is often desirable to monitor each battery in the series to prevent damage to the batteries. For instance, secondary batteries can often be damaged by dropping below a particular voltage level on discharge or by being charged above a particular voltage level during charging. As a result, each of the batteries in the battery pack can be monitored to prevent any one of the batteries from falling below a certain voltage on discharge or rising above a certain voltage upon charging. The battery monitoring requirements increase as the number of batteries in the battery pack increases. These extensive monitoring characteristics are undesirable and can be impractical for battery packs having large numbers of individual batteries.
An alternate battery pack connects battery groups in series where each of the batteries in a battery group is connected in parallel. As a result, these battery packs require several parallel connections. Each parallel connection must carry the current provided by the battery pack. As the current level to be provided by the battery pack increases, the size of these parallel connections must be increased. The current requirements needed to power a vehicle cause these parallel connections to be undesirably large and heavy. The large size of these parallel connections makes these battery packs impractically large and heavy for use in powering vehicles.
For the above reasons there is a need for a battery pack that is suitable for use in powering vehicles.